The present invention relates to a belt drive comprising a toothed belt and a toothed pulley, with the toothed belt having a toothed side on which are formed guide surfaces that are disposed along a line that extends in the longitudinal direction of the toothed belt, with the guide surfaces extending transverse to the teeth and grooves of the belt, whereby when the belt rotates about the toothed pulley, in order to provide lateral guidance for the belt the guide surfaces rest against corresponding abutment surfaces of the toothed pulley that extend transverse to the teeth of the pulley.
Normally, as toothed belts rotate about a toothed pulley, they are guided on the sides by lateral flanges of the toothed pulley. However, there are also toothed belt drives, for example where the toothed belt is used as a transport member in conveying units, where the toothed pulley cannot have flanges that project laterally beyond the toothed belt. For this purpose (see for example U.S. Pat. No. 2,770,977), a self-guiding toothed belt is known where a strip-like guide rib is disposed along the center line of the toothed side of the belt, with this guide rib engaging in a conforming annular groove on the center of the toothed peripheral surface of the pulley, or where conversely the toothed side of the belt is split into two rows of teeth by a guide groove that extends in the longitudinal direction of the belt, and a circumferential rib of the toothed pulley engages this groove; as a result, the toothed belt can also be laterally guided on the toothed pulley without flanges. However, a drawback of this heretofore known toothed belt is that the strip-like guide rib of the belt must be compressed on the curved inner side of the toothed belt as the belt rotates about the pulley. Despite the notches that are provided on the guide rib of the known toothed belt, this adversely affects the desired soft flexibility of the belt, and leads to an unfavorable operating behavior of the belt on the pulley. The known toothed belt has the particular drawback that as a consequence of the strip-like guide rib, or also due to the longitudinally extending guide groove of the belt, the force transfer surface on the surfaces of the teeth of the belt is reduced, so that in order to be able to transfer the same drive power as was possible without the guide rib or guide groove, the toothed belt must be made wider, which makes the belt more expensive and as a consequence of which the belt also rotates about the pulley with greater noise.
It is therefore an object of the present invention to provide a belt drive of the aforementioned general type that prevents a toothed belt from leaving the sides of a toothed pulley without utilizing the guide rib or guide groove of the heretofore known, self-guiding toothed belt, and that in so doing avoids the previous reduction of the force transfer surface caused by the known guide rib or groove.